It is becoming more and more common to use multi-chamber medicament containers in medicament delivery devices such as injectors. The reason for this is that the medicament can be stored for much longer time periods without being degraded in comparison with medicament dissolved in some liquid.
Thus the medicament and the liquid are kept in different compartments in the medicament container and are mixed just before use by moving a dividing wall or stopper such that the compartments can communicate with each other.
However, the multi-chamber medicament containers entail more handling steps before a dose of medicament can be injected in that the plunger rod of the injector has to move the stopper of the medicament container in order to initiate the mixing.
A number of solutions have been proposed for obtaining the mixing, from manual operation such as bringing together two parts of the injector to an automatic operation. The first is described in EP 0 288 443 in which a front cover of the injector is rotated whereby a medicament powder chamber is pushed against a plunger, which in turn breaks an aluminium membrane such that liquid is mixed with the powder.
An example of an automatic mixing function is disclosed in WO 2006/080893 wherein the spring actuated plunger rod can be pushed automatically a certain first distance, after which it is stopped. The plunger rod can then be released again and travel a certain second distance. During the first distance the mixing is performed and during the second distance the injection is performed.
Some users/patients prefer to attach a delivery member as a needle to the multi-chamber container before the mixing is performed, when the medicament is of such a kind that allows it. Also some multi-chamber containers may be syringes with an already inbuilt needle.